Video recordings sounding like the Chipmunks

[Canephins]

Took my son to see The Wiggles last night. Every video I recorded during the show sounds like Alvin and The Chipmunks. This has only happened on the videos I recorded in there and not on any other videos, recorded before or after those.

https://www.facebook.com/photo.php?v=10151098332919721

Any clues as to what happened?